The present invention relates generally to a compression brake system that provides retarding horsepower in an internal combustion engine, and particularly to a compression brake system using compressed engine oil to actuate actuator pistons that open exhaust valves at predetermined times.
Compression or decompression brake systems are commonly known and used in internal combustion engines for trucks and other vehicles. Generally, a compression brake augments the conventional vehicle brake system thereby protecting the conventional brake system from excessive wear. Two well known compression brakes are a lost motion design and an electro-mechanical design. The lost-motion brake utilizes and additional lobe on the engine""s cam to open the exhaust valve when needed. The electro-mechanical brake generally uses high pressure or compressed engine oil or fluid to activate slave pistons that open the exhaust valves.
As is know by those of skill in the art, the basic function of the decompression brake is to open an exhaust valve of a given cylinder at the end of the compression cycle when there is compressed air in the cylinder. The opening of the exhaust valve allows the power cylinder to xe2x80x9cdecompressxe2x80x9d and thus removes energy. By allowing the compressed gas within the cylinder to be purged prematurely through the open exhaust valve, the mechanical energy that was required to compress the gas can be wasted through the open exhaust valve, instead of being transferred back into the engine during the ensuing xe2x80x9cpower stroke.xe2x80x9d As a result, the engine absorbs and dissipates more energy than it otherwise normally would and thus provides retarding horsepower to the vehicle. This allows the vehicle to be slowed down. Typically, this process only occurs when the brake function is armed and then activated by the driver removing their foot from the accelerator pedal. When the input signal conditions are right, the fuel injectors stop supplying fuel to the power cylinders and the brake cycle begins.
In prior art engine compression brakes, opening the exhaust valve at, or near, the conclusion of the compression stroke required the application of axial force to the exhaust valve thereby causing the valve to open. In at least one type of prior art engine, mechanical force required to overcome the exhaust valve spring and to open the valve was provided by an actuator piston located xe2x80x9cabovexe2x80x9d or extant the exhaust valve stem and to which compressed engine oil was delivered, hydraulically opening the valve by pulsing the actuator piston at predetermined times.
These prior art hydraulic engine compression braking systems often require their own high-pressure oil systems, fast-acting actuators and precise timing in order to open the exhaust valve when the piston is at or near the top of the compression stroke. Some of these prior art engines also use pressurized engine oil to control the opening of the diesel fuel injectors, requiring two separate complex, high-pressure engine oil systems that both deliver pulses of high-pressure engine oil. Eliminating at least one of the complex, high-pressure oil control systems in such prior art engines would yield a higher-reliable engine compression braking system at a reduced cost.
The present invention provides a method and apparatus for engine compression braking for an internal combustion engine that uses hydraulic-fluid-actuated fuel injectors, where the engine compression braking can be provided by diverting or re-routing hydraulic fluid that would normally open the fuel injectors, to slave engine compression brake actuator pistons which are mechanically coupled to the exhaust valves so as to cause the exhaust valves to open at the time that the fuel injectors would have been opened to inject fuel.
There is provided a method for compression engine braking in an internal combustion engine, having a source of pressurized fluid for a hydraulically-actuated fuel injector, comprising the steps of activating compression engine braking mode, generating a diverter valve actuation signal in an engine computer, actuating the diverter valve based on the diverter valve actuation signal thereby diverting the pressurized fluid to the fuel injector towards a slave piston, actuating the slave piston via the diverted high pressure fluid, and actuating an exhaust valve, via the slave piston, for a predetermined amount of time at or near the top of a compression stroke via translation of the slave piston movement to thereby vent compressed gases in a combustion chamber to the atmosphere.
In an alternate embodiment, the method for compression engine braking in an internal combustion engine further comprises actuating a diverter valve based on a diverter valve actuation signal thereby diverting the pressurized fluid from the fuel injector towards a stroke limiter piston. The stroke limiter piston is then actuated via the diverted high pressure fluid. Next, the slave piston is actuated by translating the movement of the stroke limiter piston via hydraulic coupling means between the stroke limiter and the slave piston. As before, the exhaust valve is actuated for a predetermined amount of time at or near the top of a compression stroke, by translation of the slave piston movement, to thereby vent compressed gases in a combustion chamber to the atmosphere.
In another embodiment, there is provided a compression engine brake for an internal combustion engine having a source of pressurized fluid for at least one hydraulically-actuated fuel injector, at least one fuel injector control valve for selectively delivering pressurized fluid to a corresponding fuel injector, at least one exhaust valve through which combustion chamber gases can travel from the combustion chamber to the atmosphere, and an engine computer for monitoring and controlling engine functions. The engine compression brake comprises a diverter control valve for diverting pressurized fluid from the fuel injector in response to a diverter control valve actuation signal from the engine computer, and a slave piston for opening the exhaust valve in response to the diverted pressurized fluid to thereby vent compressed gases in a combustion chamber to the atmosphere.
In another alternate embodiment, there is provided a compression engine brake for an internal combustion engine having a source of pressurized fluid for at least one hydraulically-actuated fuel injector, at least one fuel injector control valve for selectively delivering pressurized fluid to a corresponding fuel injector, at least one exhaust valve through which combustion chamber gases can travel from a combustion chamber to the atmosphere, and an engine computer for monitoring and controlling engine functions. The engine compression brake comprises a diverter control valve for diverting pressurized fluid from the fuel injector in response to a diverter control valve actuation signal from the engine computer, a stroke limiter piston having an input face for receiving the diverted pressurized fluid and an output face such that upon the diversion of the pressurized fluid to the stroke limiter piston input face, the stroke limiter piston is displaced, and a slave piston hydraulically coupled to the stroke limiter piston via the output face such that the stroke limiter piston displacement displaces the slave piston which in turn actuates and opens a corresponding exhaust valve at substantially the end of the engine""s compression stroke to vent compressed gases from the combustion chamber to the atmosphere.
The following drawings and description set forth additional advantages and benefits of the invention. More advantages and benefits will be obvious from the description and may be learned by practice of the invention.